Improved method of producing- white pigments from lead



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JOHNGALLEMORE DA LE AND EDWARD MILNER, OF WA RRlNGTON,

/ ENGLAND.

Letters Patent No. 85,796, dated J a-nuary' 12, 1869.

-1'he Schedule referred to in these Letters Patent and making part of the same.

To all whmn it may concern Be it known that we, J OHN GALLEMORE Dana, and EnwAnnMrLsER, ofWarrington, inthe county of Lancaster, and Kingdom of England, have invcntcd a now and useful Improved Method of Producing Whitc Pigments fiOill Lead; and we do hereby declare that tho following is a full and exact dcscl'iption thereof; .that

is to say,

Our invention relatcsto an improved method of producing white pigments ti-om lead, and consists,

.First, in taking the oxides of lead, commonly known as lithargc and massicot, and treating them, in a linclyground state and under constant agitation, with a solution of a, chloride of the nlhalies or alkaline oar-tbs. After-one 'or two days contact, wc .ibtain an cx'cccdingly white and floccnlent cmnpound, which, after being washed ti'om any adhering soluble snlinc matter, is in a state to be used, as hereafter dcscribcd in the third part. We do not bind onrsclvcs to any particular proportions of litharge and chloride salt, but we may state that we find a mixture of sixty parts of watcr with ten parts of'lithargc and one part chloride of sodium, barium, or calcium, to'answer wcll.

Secondly, instead of the process above described, wc prepare hydlatcdcoxide of load byany-ofthc well-known methods, that is to say, by the solution of load-ores, litharge, or metallic lead, in any suitable acid, and subsequent precipitation by an alkali or alkaline carth. For instance, the ordinary lead-ore, known as galcna, may bedissolved in hydrochloric acid, and the hydrated 0xide of lead-fully precipitated from the resulting chloride by lime; or sulphate of load, obtained as a lye-product in several manufacturing-precesses, may be treated with soda or any suitable alkaline solution, whereby it is docomposcd, and the hydrated oxide of lead is produced. The hydrated oxide of lead, by whatever process prepared, after being freed, by washing, from any soluble salinc matter, is ready to be treated as next described. Thirdly, we now take the compound, made as described infour first part, hydrated oxidesof load, or mixtures of any proportion of them, and add sufficient water to form a. thin paste, which is put into a'suitable vcssel, either with the addition of from one to five per cent. of acetic acid oracetate of lead, nitric acid or sub-nitrate of lead, or not, as may be found desirable,

the said vessel being closed, and fitted with machinery to keep the mi.\tnrc in constant agitation. Carbonic acid is now passed into this vessel, eithernnder pressurc or othcrwisc, when it is rapidly absorbed, and the \vholc mass, or ncarly so, after the lapse of three or four days, will bc found convcrtcd into carbonate of load, possessing grcat body and opacity. When the conversion is dccnicd oomph-to, it is'well washed, and, if ncccssary, grouml and levigatcd, to frec' it from any lnnl .-coinposcd lithargc, which may be again trcatcd as before doscriln-d. 'lhc lcvigatcd pigment is then dricd, and may be used for any of the purposes for which the so-called whitc load ofconnnerw is applicable.

l. The trcatmcntot' the material obtained as specificd in thc first part, (which is a very basic chloride of lead,) with carbonic acid preferably in conjunction with small quantitics of either acetic acid, acetate of lead, nitric acid, or nitrate of lead. The pigment obtained is a vhhnm-arhonatcof lead, the amount of chlorine in combination being detcrmined by the quantity of salinc or earthy chloride used in the first treatment of thc lcad oxides.

2. The treatment of pure hydrated oxide of load, by

whatever process obtained, with carbonic acid, preferably in conjunction with either acetic acid, acetate of lead, nitric acid, or nitrate of lead, whereby a pigment answering to the ordinary white lead of commerce is obtained, oi: a pure monocarbonate, according to the lcngth of time the mixturcis exposed to the action ofthc carbonic acid.

3. Any mixture of theaiorementioned basic chlorideand hydrated oxidc of lead, before treatment with carbonic acid, or any mixture of the finished compounds to bc nscd as pigments that may be found desirable! Done at Manchester, England, this30th day of Septcmbcr, A. l'). 1868.

JOHN GALLEMORE DALE. EDWARD MILNER. Witnesses:

G. SEPTIM B HUGHES,

. Patent Agent, 4

.11 Bicclqfriwrs Street, Mmwhesm'. Unans WM. ()oimrns,

ll .Blcchfrmrs' Street, M anclwster. 

